During a switching operation of a circuit breaker, an overvoltage or an inrush current may occur and affect a system. Therefore, a power switching control device that controls switching of a circuit breaker in a phase where an overvoltage or an inrush current can be suppressed is conventionally used.
At the time of activation of a circuit breaker, before the contacts are mechanically brought into contact with each other, pre-arcing due to dielectric breakdown occurs between contacts of the circuit breaker and the contacts are conducted with each other. Therefore, when the circuit breaker is to be activated, it is necessary to set the phase of an electrical activation point as a target phase and predict a pre-arcing time to determine a target closing clock time. The pre-arcing time is a duration time of pre-arcing.
In a conventional power switching control device, the pre-arcing time at the time of activation of a circuit breaker is calculated from a rate of decrease of dielectric strength (RDDS) of the circuit breaker and a system voltage. The RDDS is assumed to be a constant value (Patent Literature 1).